Serializing a DataTable with an IPAddress column

Question

I'm using C# with .NET 3.5.

I am using the System.Configuration.ApplicationSettingsBase class to load and save application settings. One of the settings I would like to preserve is an in-memory System.Data.DataTable. The DataTable contains just two columns of type UInt32 and System.Net.IPAddress, respectively. When I call the Save() function on the ApplicationSettingsBase, I get the following exception:

InvalidOperationException: System.Net.IPAddress cannot be serialized because it does not have a parameterless constructor.

If I just use a System.Net.IPAddress object as the setting instead of the DataTable, I do not have a problem. There's something about it being in the DataTable that is causing the exception.

Any ideas what might be going on? Any ideas on how to fix it?

Answer 1

The error explains the problem- store it as a string instead. If you need to use the IPAddress class you can use ToString and Parse to convert between the two. The error will be due to the way DataTable does the serialization.

Try this code:

IPAddress ip = IPAddress.Parse("192.168.0.1");
XmlSerializer serializer = new XmlSerializer(typeof(IPAddress));  
MemoryStream ms = new MemoryStream();
serializer.Serialize(ms, ip);

Then try this:

IPAddress ip = IPAddress.Parse("192.168.0.1");
BinaryFormatter serializer = new BinaryFormatter();
MemoryStream ms = new MemoryStream();
serializer.Serialize(ms, ip);

You will see that when you put the IPAddress object in a datatable the XmlSerializer is used by default.

Interestingly try changing the RemotingFormat property to binary, I believe this may fix the issue. DataTable.RemotingFormat

Answer 2

I think the XmlElementAttribute might solve your problem